A) \[6\Omega \]
B) \[4\Omega \]
C) \[2.9\Omega \]
D) \[3.1\Omega \]
Correct Answer: C
Solution :
\[\eta =\frac{{{P}_{o}} \left( output power \right)}{{{P}_{i}} \left( input power \right)}\] \[{{P}_{o}}=\eta {{P}_{i}}={{P}_{i}}\frac{30}{100}\times 50\times 12\] \[{{\operatorname{P}}_{o}}=180W\] \[\operatorname{Power} loss in heating = {{P}_{i}}-{{P}_{o}}\] \[{{P}_{\operatorname{lass}}}=600-180=420\] \[{{P}_{\operatorname{L}}}=420={{\operatorname{I}}^{2}}R\] \[R=2.9\Omega \operatorname{I}=12\operatorname{A}\]
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